Of the more than 2600 known naturally occurring organohalogen compounds, more than 1500 contain chlorine. These organochlorines, which range in structural intricacy from the ubiquitous fungal and plant metabolite chloromethane to the complex life-saving antibiotic vancomycin, are produced by marine and terrestrial plants, bacteria, fungi, lichens, insects, marine animals (sponges, sea hares, nudibranchs, gorgonians, tunicates), some higher animals, and a few mammals. New examples are continually being discovered and the total number of natural organohalogens may surpass 3000 by the turn of the century.